The cast of K-ON!, their seiyuu, and the at times optimistic “official” 2D versions are compared in this image.

Their identities:

Sawako Yamanaka: Asami Sanada

Nodoka Manabe: Chika Fujitō

Ritsu Tainaka: Satomi Satō

Mio Akiyama: Yōko Hikasa

Yui Hirasawa: Aki Toyosaki

Tsumugi Kotobuki: Minako Kotobuki

Ui Hirasawa: Madoka Yonezawa

Azusa Nakano: Ayana Taketatsu

2ch’s microscopic analysis reveals some problems with the perspective of the illustration (though some whisper that they are actually a dig at Kotobuki’s height), but you are perhaps better spared these…

Damn my kanji input software, I sometimes mix up whenever I'm trying to type Japanese or Chinese. The one I typed above 壽 was the traditional Chinese version, this 寿 (with less strokes) is the Japanese one.

Someone obviously forgot just how much taller Toyosaki Aki is compared to the rest, even if she is bending slightly in the picture - 169cm vs Kotobuki Minako, who I think is the second tallest of the main girls, at 158cm. Such an old picture of Toyosaki, too.